Methods and systems for controlling current in electrochemical processing of microelectronic workpieces

ABSTRACT

A method and system for electrolytically processing a microelectronic workpiece. In one embodiment, the method includes contacting the workpiece with an electrolytic fluid, positioning one or more electrodes in electrical communication with the workpiece, directing an electrical current through the electrolytic fluid from the electrodes to the workpiece or vice versa, and actively changing a distribution of the current at the workpiece during the process. For example, the current can be changed such that a current ratio of at least one electrical current to the sum of the electrical currents shifts from a first current ratio value to a second current ratio value. Accordingly, the current applied to the workpiece can be adjusted to achieve a target shape for a conductive layer on the workpiece, or to account for temporally and/or spatially varying characteristics of the electrolytic process.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to ProvisionalApplication No. 60/294,690, filed May 30, 2001, which is incorporatedherein in its entirety by reference.

TECHNICAL FIELD

[0002] This application relates to methods and systems for enhancing theperformance of plating and other electrochemical processes.

BACKGROUND

[0003] Microelectronic devices, such as semiconductor devices and fieldemission displays, are generally fabricated on and/or in microelectronicworkpieces using several different types of machines (“tools”). Manysuch processing machines have a single processing station that performsone or more procedures on the workpieces. Other processing machines havea plurality of processing stations that perform a series of differentprocedures on individual workpieces or batches of workpieces. In atypical fabrication process, one or more layers of conductive materialsare formed on the workpieces during deposition stages. The workpiecesare then typically subject to etching and/or polishing procedures (.e.,planarization) to remove a portion of the deposited conductive layersfor forming electrically isolated contacts and/or conductive lines.

[0004] Plating tools that plate metals or other materials on theworkpieces are becoming an increasingly useful type of processingmachine. Electroplating and electroless plating techniques can be usedto deposit copper, solder, permalloy, gold, silver, platinum and othermetals onto workpieces for forming blanket layers or patterned layers. Atypical copper plating process involves depositing a copper seed layeronto the surface of the workpiece using chemical vapor deposition (CVD),physical vapor deposition (PVD), electroless plating processes, or othersuitable methods. After forming the seed layer, a blanket layer orpatterned layer of copper is plated onto the workpiece by applying anappropriate electrical potential between the seed layer and an anode inthe presence of an electroprocessing solution. The workpiece is thencleaned, etched and/or annealed in subsequent procedures beforetransferring the workpiece to another processing machine.

[0005]FIG. 1 illustrates an embodiment of a single-wafer processingstation 1 that includes a container 2 for receiving a flow ofelectroplating solution from a fluid inlet 3 at a lower portion of thecontainer 2. The processing station 1 can include an anode 4, aplate-type diffuser 6 having a plurality of apertures 7, and a workpieceholder 9 for carrying a workpiece 5. The workpiece holder 9 can includea plurality of electrical contacts for providing electrical current to aseed layer on the surface of the workpiece 5. The seed layer acts as acathode when it is biased with a negative potential relative to theanode 4. In operation the electroplating fluid flows around the anode 4,through the apertures 7 in the diffuser 6 and against the platingsurface of the workpiece 5. The electroplating solution is anelectrolyte that conducts electrical current between the anode 4 and thecathodic seed layer on the surface of the workpiece 5. Therefore, ionsin the electroplating solution are reduced at the surface of theworkpiece 5 to form a metal film.

[0006] The plating machines used in fabricating microelectronic devicesmust meet many specific performance criteria. For example, manyprocesses must be able to form small contacts in vias that are less than0.5 μm wide, and are desirably less than 0.1 μm wide. The plated metallayers accordingly often need to fill vias or trenches that are on theorder of 0.1 μm wide, and the layer of plated material should also bedeposited to a desired, uniform thickness across the surface of theworkpiece 5. One factor that influences the uniformity of the platedlayer is the current density at the workpiece. Current density isinfluenced by the mass transfer of electroplating solution at thesurface of the workpiece. This parameter is generally influenced by thevelocity of the flow of the electroplating solution perpendicular to thesurface of the workpiece. Other factors that influence the currentdensity at the workpiece are the design of the electroplating chamber,the position of the anodes, the initial seed layer resistance and thecurrent applied to the anodes.

[0007] One concern of existing electroplating equipment is providing auniform mass transfer at the surface of the workpiece. Referring to FIG.1, existing plating tools generally use the diffuser 6 to enhance theuniformity of the fluid flow perpendicular to the face of the workpiece.Although the diffuser 6 improves the uniformity of the fluid flow, itproduces a plurality of localized areas of increased flow velocityperpendicular to the surface of the workpiece 5 (indicated by arrows 8).The localized areas generally correspond to the position of theapertures 7 in the diffuser 6. The increased velocity of the fluid flownormal to the substrate in the localized areas increases the masstransfer of the electroplating solution in these areas. This typicallyresults in faster plating rates in the localized areas over theapertures 7. Although many different configurations of apertures havebeen used in plate-type diffusers, these diffusers may not provideadequate uniformity for the precision required in many currentapplications.

[0008] Another concern of existing plating tools is that the diffusionlayer in the electroplating solution adjacent to the surface of theworkpiece 5 can be disrupted by gas bubbles or particles. For example,bubbles can be introduced to the plating solution by the plumbing andpumping system of the processing equipment, or they can evolve frominert anodes. Consumable anodes are often used to prevent or reduce theevolvement of gas bubbles in the electroplating solution, but theseanodes erode and they can form a passivated film surface that must bemaintained. Consumable anodes, moreover, often generate particles thatcan be carried in the plating solution. As a result, gas bubbles and/orparticles can flow to the surface of the workpiece 5, which disrupts theuniformity and affects the quality of the plated layer.

[0009] Still another challenge of plating uniform layers is providing adesired electrical field at the surface of the workpiece 5. Thedistribution of electrical current in the plating solution is a functionof the uniformity of the seed layer across the contact surface, theresistance of the seed layer, the configuration/condition of the anode,and the configuration of the chamber. However, the current densityprofile on the plating surface can change. For example, the currentdensity profile typically changes during a plating cycle because platingmaterial covers the seed layer, or it can change over a longer period oftime because the shape of consumable anodes changes as they erode andthe concentration of constituents in the plating solution can change.Therefore, it can be difficult to maintain a desired current density atthe surface of the workpiece 5 and can accordingly be difficult to formuniform void-free plated layers. In one particular example, the currentdensity can be significantly higher near the junctions between thecontact elements and the workpiece 5 than at points distant from thesejunctions, an effect referred to in the industry as the “terminaleffect.” This can result in electroplated layers that (a) are notuniformly thick and/or (b) contain voids and/or (c) non-uniformlyincorporating impurities or defects. Both of these characteristics tendto reduce the effectiveness and/or reliability of the devices formedfrom the workpiece 5.

SUMMARY

[0010] The present invention is directed toward methods and systems forelectrolytically processing microelectronic workpieces. One aspect ofseveral embodiments of the invention includes electrolyticallydepositing conductive material on a microelectronic workpiece byapplying current to the workpiece through an electrolytic fluid from oneor more electrodes. The distribution of current in the electrolyticfluid is actively changed during the course of the process. For example,in one embodiment, the current is applied by a plurality of electrodesin a manner that can account for different plating characteristics atdifferent portions of the workpiece, and the current applied toindividual electrodes is changed to account for changes in behavior asthe thickness of the conductive material on the workpiece increases. Asa result, conductive materials such as copper are deposited on theworkpiece at a uniform current density or other desired current densityto provide a conductive layer having the desired properties. Severalembodiments of the present invention accordingly apply the current tothe individual electrodes to counteract the terminal effect between thecontact elements and the workpiece. Additional embodiments of theinvention compensate for irregularities in the seed layers or otheraspects of single-wafer electrochemical deposition techniques to inhibitvoids and produce plated layers with a desired thickness.

[0011] The current applied to the electrodes is varied in a variety ofmanners. For example, in one embodiment the current is varied such thatthe ratio of the current applied to one electrode relative to thecurrents provided by all the electrodes changes over time. This ratiohas one value while features in a seed layer of the workpiece arefilled, and another value while a blanket layer is applied to the filledfeatures. In another arrangement, the current is applied such that thecurrent density per unit area of the microelectronic workpiece varies byless than about ten percent of a 3σ value across the surface of theworkpiece.

[0012] In still further embodiments, the current is varied in othermanners. For example, in one embodiment the current is varied to createa domed or dished blanket layer on an initially flat seed layer, or aflat blanket layer on an initially domed or dished seed layer. Inanother embodiment, current is provided at an opposite polarity to atleast one of the electrodes to either remove material from the workpieceor attract material that would otherwise attach to the workpiece, again,to form a conductive layer having a desired shape and/or uniformity.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a schematic diagram of an electroplating chamber inaccordance with the prior art.

[0014]FIG. 2 is an isometric view of an electroprocessing machine havingelectroprocessing stations for processing microelectronic workpieces inaccordance with an embodiment of the invention.

[0015]FIG. 3 is a cross-sectional view of an electroprocessing stationhaving a processing chamber for use in an electroprocessing machine inaccordance with an embodiment of the invention. Selected components inFIG. 3 are shown schematically.

[0016]FIG. 4 is an isometric view showing a cross-sectional portion of aprocessing chamber taken along line 4-4 of FIG. 8A.

[0017] FIGS. 5A-5D are cross-sectional views of a distributor for aprocessing chamber in accordance with an embodiment of the invention.

[0018]FIG. 6 is an isometric view showing a different cross-sectionalportion of the processing chamber of FIG. 4 taken along line 6-6 of FIG.8B.

[0019]FIG. 7A is an isometric view of an interface assembly for use in aprocessing chamber in accordance with an embodiment of the invention.

[0020]FIG. 7B is a cross-sectional view of the interface assembly ofFIG. 7A.

[0021]FIGS. 8A and 8B are top plan views of a processing chamber thatprovide a reference for the isometric, cross-sectional views of FIGS. 4and 6, respectively.

[0022] FIGS. 9A-9D are flow diagrams illustrating processes inaccordance with embodiments of the invention.

[0023]FIG. 10A is a table illustrating predicted electrode currents as afunction of initial seed layer thickness for instantaneously uniformdeposition, simulating a multi-stage deposition process in accordancewith an embodiment of the invention.

[0024]FIG. 10B is a graph illustrating the predicted electrode currentsas a function of initial seed layer thickness based on the table of FIG.10A.

[0025]FIG. 11 illustrates predicted electrode currents as a function oftime for a multi-stage process in accordance with an embodiment of theinvention.

[0026]FIG. 12 is a graphical comparison of film non-uniformity as afunction of film thickness for an existing single-step plating processand a multi-stage process in accordance with an embodiment of theinvention.

[0027]FIG. 13 is a graph of predicted current density as a function oflocation on a microelectronic workpiece for a multi-stage process inaccordance with an embodiment of the invention.

[0028]FIG. 14 is a graph of predicted current density as a function oflocation on a microelectronic workpiece for an existing single-stageprocess.

[0029]FIG. 15 is a graph of experimentally determined initial and finalconductive layer thicknesses for a microelectronic workpiece processedin accordance with an embodiment of the invention.

[0030]FIG. 16 is a graph illustrating experimentally determined initialand final thicknesses for a concave conductive layer deposited inaccordance with an embodiment of the invention.

DETAILED DESCRIPTION

[0031] The following description discloses the details and features ofseveral embodiments of electrochemical reaction vessels for use inelectrochemical processing stations and integrated tools to processmicroelectronic workpieces. The term “microelectronic workpiece” is usedthroughout to include a workpiece formed from a substrate upon whichand/or in which microelectronic circuits or components, data storageelements or layers, and/or micro-mechanical elements are fabricated. Itwill be appreciated that several of the details set forth below areprovided to describe the following embodiments in a manner sufficient toenable a person skilled in the art to make and use the disclosedembodiments. Several of the details and advantages described below,however, may not be necessary to practice certain embodiments of theinvention. Additionally, the invention can also include additionalembodiments that are within the scope of the claims, but are notdescribed in detail with respect to FIGS. 2-16.

[0032] The operation and features of electrochemical reaction vesselsare best understood in light of the environment and equipment in whichthey can be used to electrochemically process workpieces (e.g.,electroplate and/or electropolish). As such, embodiments of integratedtools with processing stations having the electrochemical reactionvessels are initially described with reference to FIGS. 2 and 3 (SectionA). The details and features of several embodiments of electrochemicalreaction vessels and methods for mechanically controlling theelectrochemical processing current during processing are then describedwith reference to FIGS. 4-8B (Section B). Further details of methods forelectrically controlling the current during electrochemical processingare described with reference to FIGS. 9A-16 (Section C).

[0033] A. Selected Embodiments of Integrated Tools with ElectrochemicalProcessing Stations

[0034]FIG. 2 is an isometric view of a system, such a processing machine100, having an electrochemical processing station 120 in accordance withan embodiment of the invention. A portion of the processing machine 100is shown in a cut-away view to illustrate selected internal components.In one aspect of this embodiment, the processing machine 100 includes acabinet 102 having an interior region 104 defining an interior enclosurethat is at least partially isolated from an exterior region 105. Thecabinet 102 also includes a plurality of apertures 106 (only one shownin FIG. 1) through which microelectronic workpieces 101 can ingress andegress between the interior region 104 and a load/unload station 110.

[0035] In one embodiment, the load/unload station 110 has two containersupports 112 that are each housed in a protective shroud 113. Thecontainer supports 112 are configured to position workpiece containers114 relative to the apertures 106 in the cabinet 102. The workpiececontainers 114 each house a plurality of microelectronic workpieces 101in a “mini” clean environment for carrying a plurality of workpiecesthrough other environments that are not at clean room standards. Each ofthe workpiece containers 114 is accessible from the interior region 104of the cabinet 102 through the apertures 106.

[0036] In one embodiment, the processing machine 100 also includes aplurality of electrochemical processing stations 120 and a transferdevice 130 in the interior region 104 of the cabinet 102. In one aspectof this embodiment, the processing machine 100 is a plating tool thatalso includes clean/etch capsules 122, electroless plating stations,annealing stations, and/or metrology stations.

[0037] The transfer device 130 includes a linear track 132 extending ina lengthwise direction of the interior region 104 between the processingstations. In one aspect of this embodiment, the transfer device 130further includes a robot unit 134 carried by the track 132. In theparticular embodiment shown in FIG. 2, a first set of processingstations is arranged along a first row R₁-R₁ and a second set ofprocessing stations is arranged along a second row R₂-R₂. The lineartrack 132 extends between the first and second rows of processingstations, and the robot unit 134 can access any of the processingstations along the track 132.

[0038] In a further aspect of this embodiment, the processing machine100 includes a controller 140 (such as a computer) that coordinates theactivities of the load/unload station 110, the processing stations 120,and the transfer device 130. In a particular embodiment, the controller140 includes an input device 141 (such as a keyboard), a graphical userinterface 142 (such as an LCD screen) and a processor (not visible inFIG. 2). The controller 140 also includes a computer operable medium,such as a memory or a computer-readable medium (for example, a harddisk, floppy disk or CD). In one embodiment, the computer operablemedium includes instructions for directing the operation of theload/unload station 110 and the transfer device 130 to move workpiecesinto and out of the processing stations 120. In one aspect of thisembodiment, the computer operable medium also includes instructions fora controller 140 regulating the electrical current(s) applied to theworkpieces processed in the processing stations 120, as described ingreater detail below with reference to FIGS. 9A-16.

[0039]FIG. 3 illustrates an embodiment of an electrochemical-processingchamber 120 having a head assembly 150 and a processing chamber 200. Thehead assembly 150 includes a spin motor 152, a rotor 154 coupled to thespin motor 152, and a contact assembly 160 carried by the rotor 154. Therotor 154 can have a backing plate 155 and a seal 156. The backing plate155 can move transverse to a workpiece 101 (arrow T) between a firstposition in which the backing plate 155 contacts a backside of theworkpiece 101 (shown in solid lines in FIG. 3) and a second position inwhich it is spaced apart from the backside of the workpiece 101 (shownin broken lines in FIG. 3). The contact assembly 160 can have a supportmember 162, a plurality of contacts 164 carried by the support member162, and a plurality of shafts 166 extending between the support member162 and the rotor 154. The contacts 164 can be ring-type spring contactsor other types of contacts that are configured to engage a portion ofthe seed-layer on the workpiece 101. Commercially available headassemblies 150 and contact assemblies 160 can be used in theelectroprocessing chamber 120. Particular suitable head assemblies 150and contact assemblies 160 are disclosed in U.S. Pat. Nos. 6,228,232 and6,080,691; and U.S. application Ser. Nos. 09/385,784; 09/386,803;09/386,610; 09/386,197; 09/501,002; 09/733,608; and 09/804,696, all ofwhich are herein incorporated by reference.

[0040] The processing chamber 200 includes an outer housing 202 (shownschematically in FIG. 3) and a reaction vessel 204 (also shownschematically in FIG. 3) in the housing 202. The reaction vessel 204carries at least one electrode (not shown in FIG. 3) and directs a flowof electroprocessing solution to the workpiece 101. Theelectroprocessing solution, for example, can flow over a weir (arrow F)and into the external housing 202, which captures the electroprocessingsolution and sends it back to a tank. Several embodiments of reactionvessels 204 are shown and described in detail with reference to FIGS.4-8B.

[0041] In operation, the head assembly 150 holds the workpiece at aworkpiece-processing site of the reaction vessel 204 so that at least aplating surface of the workpiece engages the electroprocessing solution.An electrical field is established in the solution by applying anelectrical potential between the plating surface of the workpiece viathe contact assembly 160 and one or more electrodes in the reactionvessel 204. For example, the contact assembly 160 can be biased with anegative potential with respect to the electrode(s) in the reactionvessel 204 to plate materials onto the workpiece. On the other hand, thecontact assembly 160 can be biased with a positive potential withrespect to the electrode(s) in the reaction vessel 204 to (a) de-plateor electropolish plated material from the workpiece or (b) deposit othermaterials (e.g., electrophoretic resist). In general, therefore,materials can be deposited on or removed from the workpiece with theworkpiece acting as a cathode or an anode depending upon the particulartype of material used in the electrochemical process.

[0042] B. Selected Embodiments of Reaction Vessels for Use inElectrochemical Processing Chambers

[0043] FIGS. 4-8B illustrate several embodiments of reaction vessels 204for use in the processing chamber 200. As explained above, the housing202 carries the reaction vessel 204. The housing 202 can have a drain210 for returning the processing fluid that flows out of the reactionvessel 204 to a storage tank, and a plurality of openings for receivinginlets and electrical fittings. The reaction vessel 204 can include anouter container 220 having an outer wall 222 spaced radially inwardly ofthe housing 202. The outer container 220 can also have a spiral spacer224 between the outer wall 222 and the housing 202 to provide a spiralramp (i.e., a helix) on which the processing fluid can flow downward tothe bottom of the housing 202. The spiral ramp reduces the entrainmentof gasses in the return fluid.

[0044] The particular embodiment of the reaction vessel 204 shown inFIG. 4 can include a distributor 300 for receiving a primary fluid flowF_(p) and a secondary fluid flow F₂, a primary flow guide 400 coupled tothe distributor 300 to condition the primary fluid flow F_(p,) and afield shaping unit 500 coupled to the distributor 300 to contain thesecondary flow F₂ in a manner that shapes the electrical field in thereaction vessel 204. The reaction vessel 204 can also include at leastone electrode 600 in a compartment of the field shaping unit 500 and atleast one filter or other type of interface member 700 carried by thefield shaping unit 500 downstream from the electrode. The primary flowguide 400 can condition the primary flow F_(p) by projecting this flowradially inwardly relative to a common axis A-A, and a portion of thefield shaping unit 500 directs the conditioned primary flow F_(p) towardthe workpiece. In several embodiments, the primary flow passing throughthe primary flow guide 400 and the center of the field shaping unit 500controls the mass transfer of processing solution at the surface of theworkpiece. The field shaping unit 500 also defines the shape theelectric field, and it can influence the mass transfer at the surface ofthe workpiece if the secondary flow passes through the field shapingunit. The rate at which the workpiece is rotated (typically from about20 rpm to about 100 rpm) can also be used to influence the mass transferat the surface of the workpiece.

[0045] The reaction vessel 204 can also have other configurations ofcomponents to guide the primary flow F_(p) and the secondary flow F₂through the processing chamber 200. For example, in one embodiment, thereaction vessel 204 includes a shield 580 having a central openingsurrounded by a ring-shaped, solid portion that at least limits contactbetween the fluid flow and the peripheral region of the workpiece 101(FIG. 3). In one aspect of this embodiment, the shield 580 is removedentirely or replaced with another shield having a larger or smallercentral opening to control the fluid flow passing adjacent to theperipheral region of the workpiece 101 and to influence the electricalfield in the peripheral region. In a further aspect of this embodiment,the vertical separation between the shield 580 and the workpiece 101 isalso adjusted to control the interaction between the fluid and theworkpiece 101. In one embodiment, the reaction vessel 204 also includesa diffuser (generally similar to that shown in FIG. 1) positioned in thefluid flow. The porosity/hole pattern of the diffuser is selected tofurther control the interaction between the fluid/electrical field andthe workpiece 101.

[0046] In still further embodiments, the reaction vessel 204 has otherconfigurations. The reaction vessel 204, for example, may not have adistributor in the processing chamber, but rather separate fluid lineswith individual flows can be coupled to the vessel 204 to provide adesired distribution of fluid through the primary flow guide 400 and thefield shaping unit. For example, the reaction vessel 204 can have afirst outlet in the outer container 220 for introducing the primary flowinto the reaction vessel and a second outlet in the outer container forintroducing the secondary flow into the reaction vessel 204. Each ofthese components is explained in more detail below.

[0047] FIGS. 5A-5D illustrate an embodiment of the distributor 300 fordirecting the primary fluid flow to the primary flow guide 400 and thesecondary fluid flow to the field shaping unit 500. Referring to FIG.5A, the distributor 300 can include a body 310 having a plurality ofannular steps 312 (identified individually by reference numbers 312 a-d)and annular grooves 314 in the steps 312. The outermost step 312 d isradially inward of the outer wall 222 (shown in broken lines) of theouter container 220 (FIG. 4), and each of the interior steps 312 a-c cancarry an annular wall (shown in broken lines) of the field shaping unit500 in a corresponding groove 314. The distributor 300 can also includea first inlet 320 for receiving the primary flow F_(p) and a plenum 330for receiving the secondary flow F₂. The first inlet 320 can have aninclined, annular cavity 322 to form a passageway 324 (best shown inFIG. 4) for directing the primary fluid flow F_(p) under the primaryflow guide 400. The distributor 300 can also have a plurality of upperorifices 332 along an upper part of the plenum 330 and a plurality oflower orifices 334 along a lower part of the plenum 330. As explained inmore detail below, the upper and lower orifices are open to channelsthrough the body 310 to distribute the secondary flow F₂ to the risersof the steps 312. The distributor 300 can also have otherconfigurations, such as a “step-less” disk or non-circular shapes.

[0048] FIGS. 5A-5D further illustrate one configuration of channelsthrough the body 310 of the distributor 300. Referring to FIG. 5A, anumber of first channels 340 extend from some of the lower orifices 334to openings at the riser of the first step 312 a. FIG. 5B shows a numberof second channels 342 extending from the upper orifices 332 to openingsat the riser of the second step 312 b, and FIG. 5C shows a number ofthird channels 344 extending from the upper orifices 332 to openings atthe riser of the third step 312 c. Similarly, FIG. 5D illustrates anumber of fourth channels 346 extending from the lower orifices 334 tothe riser of the fourth step 312 d.

[0049] The particular embodiment of the channels 340-346 in FIGS. 5A-5Dare configured to transport bubbles that collect in the plenum 330radially outward as far as practical so that these bubbles can becaptured and removed from the secondary flow F₂. This is beneficialbecause the field shaping unit 500 removes bubbles from the secondaryflow F₂ by sequentially transporting the bubbles radially outwardlythrough electrode compartments. For example, a bubble B in thecompartment above the first step 312 a can sequentially cascade throughthe compartments over the second and third steps 312 b-c, and then beremoved from the compartment above the fourth step 312 d. The firstchannel 340 (FIG. 5A) accordingly carries fluid from the lower orifices334 where bubbles are less likely to collect to reduce the amount of gasthat needs to cascade from the inner compartment above the first step312 a all the way out to the outer compartment. The bubbles in thesecondary flow F₂ are more likely to collect at the top of the plenum330 before passing through the channels 340-346. The upper orifices 332are accordingly coupled to the second channel 342 and the third channel344 to deliver these bubbles outward beyond the first step 312 a so thatthey do not need to cascade through so many compartments. In thisembodiment, the upper orifices 332 are not connected to the fourthchannels 346 because this would create a channel that inclinesdownwardly from the common axis such that it may conflict with thegroove 314 in the third step 312 c. Thus, the fourth channel 346 extendsfrom the lower orifices 334 to the fourth step 312 d.

[0050] Referring again to FIG. 4, the primary flow guide 400 receivesthe primary fluid flow F_(p) via the first inlet 320 of the distributor300. In one embodiment, the primary flow guide 400 includes an innerbaffle 410 and an outer baffle 420. The inner baffle can have a base 412and a wall 414 projecting upward and radially outward from the base 412.The wall 414, for example, can have an inverted frusto-conical shape anda plurality of apertures 416. The apertures 416 can be holes, elongatedslots or other types of openings. In the illustrated embodiment, theapertures 416 are annularly extending radial slots that slant upwardrelative to the common axis to project the primary flow radially inwardand upward relative to the common axis along a plurality ofdiametrically opposed vectors. The inner baffle 410 can also includes alocking member 418 that couples the inner baffle 410 to the distributor300.

[0051] The outer baffle 420 can include an outer wall 422 with aplurality of apertures 424. In this embodiment, the apertures 424 areelongated slots extending in a direction transverse to the apertures 416of the inner baffle 410. The primary flow F_(p) flows through (a) thefirst inlet 320, (b) the passageway 324 under the base 412 of the innerbaffle 410, (c) the apertures 424 of the outer baffle 420, and then (d)the apertures 416 of the inner baffle 410. The combination of the outerbaffle 420 and the inner baffle 410 conditions the direction of the flowat the exit of the apertures 416 in the inner baffle 410. The primaryflow guide 400 can thus project the primary flow along diametricallyopposed vectors that are inclined upward relative to the common axis tocreate a fluid flow that has a highly uniform velocity. In alternateembodiments, the apertures 416 do not slant upward relative to thecommon axis such that they can project the primary flow normal, or evendownward, relative to the common axis.

[0052]FIG. 4 also illustrates an embodiment of the field shaping unit500 that receives the primary fluid flow F_(p) downstream from theprimary flow guide 400. The field shaping unit 500 also contains thesecond fluid flow F₂ and shapes the electrical field within the reactionvessel 204. In this embodiment, the field shaping unit 500 has acompartment structure with a plurality of walls 510 (identifiedindividually by reference numbers 510 a-d) that define electrodecompartments 520 (identified individually by reference numbers 520 a-d).The walls 510 can be annular skirts or dividers, and they can bereceived in one of the annular grooves 314 in the distributor 300. Inone embodiment, the walls 510 are not fixed to the distributor 300 sothat the field shaping unit 500 can be quickly removed from thedistributor 300. This allows easy access to the electrode compartments520 and/or quick removal of the field shaping unit 500 to change theshape of the electric field.

[0053] The field shaping unit 500 can have at least one wall 510 outwardfrom the primary flow guide 400 to prevent the primary flow F_(p) fromcontacting an electrode. In the particular embodiment shown in FIG. 4,the field shaping unit 500 has a first electrode compartment 520 adefined by a first wall 510 a and a second wall 510 b, a secondelectrode compartment 520 b defined by the second wall 510 b and a thirdwall 510 c, a third electrode compartment 520 c defined by the thirdwall 510 c and a fourth wall 510 d, and a fourth electrode compartment520 d defined by the fourth wall 510 d and the outer wall 222 of thecontainer 220. The walls 510 a-d of this embodiment are concentricannular dividers that define annular electrode compartments 520 a-d.Alternate embodiments of the field shaping unit can have walls withdifferent configurations to create non-annular electrode compartmentsand/or each electrode compartment can be further divided into cells. Thesecond-fourth walls 510 b-d can also include holes 522 for allowingbubbles in the first-third electrode compartments 520 a-c to “cascade”radially outward to the next outward electrode compartment 520 asexplained above with respect to FIGS. 5A-5D. The bubbles can then exitthe fourth electrode compartment 520 d through an exit hole 525 throughthe outer wall 222. In an alternate embodiment, the bubbles can exitthrough an exit hole 524.

[0054] The electrode compartments 520 provide electrically discretecompartments to house an electrode assembly having at least oneelectrode and generally two or more electrodes 600 (identifiedindividually by reference numbers 600 a-d). The electrodes 600 can beannular members (e.g., annular rings or arcuate sections) that areconfigured to fit within annular electrode compartments, or they canhave other shapes appropriate for the particular workpiece (e.g.,rectilinear). In the illustrated embodiment, for example, the electrodeassembly includes a first annular electrode 600 a in the first electrodecompartment 520 a, a second annular electrode 600 b in the secondelectrode compartment 520 b, a third annular electrode 600 c in thethird electrode compartment 520 c, and a fourth annular electrode 600 din the fourth electrode compartment 520 d. As explained in U.S.application Ser. Nos. 60/206,661, 09/845,505, and 09/804,697, all ofwhich are incorporated herein by reference, each of the electrodes 600a-d can be biased with the same or different potentials with respect tothe workpiece to control the current density across the surface of theworkpiece. In alternate embodiments, the electrodes 600 can benon-circular shapes or sections of other shapes.

[0055] The field shaping unit 500 can also include a virtual electrodeunit coupled to the walls 510 of the compartment assembly forindividually shaping the electrical fields produced by the electrodes600. In the particular embodiment illustrated in FIG. 4, the virtualelectrode unit includes first-fourth partitions 530 a-530 d,respectively. The first partition 530 a can have a first section 532 acoupled to the second wall 510 b, a skirt 534 depending downward abovethe first wall 510 a, and a lip 536 a projecting upwardly. The lip 536 ahas an interior surface 537 that directs the primary flow F_(p) exitingfrom the primary flow guide 400. The second partition 530 b can have afirst section 532 b coupled to the third wall 510 c and a lip 536 bprojecting upward from the first section 532 b, the third partition 530c can have a first section 532 c coupled to the fourth wall 510 d and alip 536 c projecting upward from the first section 532 c, and the fourthpartition 530 d can have a first section 532 d carried by the outer wall222 of the container 220 and a lip 536 d projecting upward from thefirst section 532 d. The fourth partition 530 d may not be connected tothe outer wall 222 so that the field shaping unit 500 can be quicklyremoved from the vessel 204 by simply lifting the virtual electrodeunit. The interface between the fourth partition 530 d and the outerwall 222 is sealed by a seal 527 to inhibit both the fluid and theelectrical current from leaking out of the fourth electrode compartment520 d. The seal 527 can be a lip seal. Additionally, each of thesections 532 a-d can be lateral sections extending transverse to thecommon axis.

[0056] The individual partitions 530 a-d can be machined from or moldedinto a single piece of dielectric material, or they can be individualdielectric members that are welded together. In alternate embodiments,the individual partitions 530 a-d are not attached to each other and/orthey can have different configurations. In the particular embodimentshown in FIG. 4, the partitions 530 a-d are annular horizontal members,and each of the lips 536 a-d are annular vertical members arrangedconcentrically about the common axis.

[0057] The walls 510 and the partitions 530 a-d are generally dielectricmaterials that contain the second flow F₂ of the processing solution forshaping the electric fields generated by the electrodes 600 a-d. Thesecond flow F₂, for example, can pass (a) through each of the electrodecompartments 520 a-d, (b) between the individual partitions 530 a-d, andthen (c) upward through the annular openings between the lips 536 a-d.In this embodiment, the secondary flow F₂ through the first electrodecompartment 520 a can join the primary flow F_(p) in an antechamber justbefore the primary flow guide 400, and the secondary flow through thesecond-fourth electrode compartments 520 b-d can join the primary flowF_(p) beyond the top edges of the lips 536 a-d. The flow ofelectroprocessing solution then flows over a shield weir attached at rim538 and into the gap between the housing 202 and the outer wall 222 ofthe container 220 as disclosed in International Application No.PCT/US00/10120, incorporated herein by reference. The fluid in thesecondary flow F₂ can be prevented from flowing out of the electrodecompartments 520 a-d to join the primary flow F_(p) while still allowingelectrical current to pass from the electrodes 600 to the primary flow.In this alternate embodiment, the secondary flow F₂ can exit thereaction vessel 204 through the holes 522 in the walls 510 and the hole525 in the outer wall 222. In still additional embodiments in which thefluid of the secondary flow does not join the primary flow, a duct canbe coupled to the exit hole 525 in the outer wall 222 so that a returnflow of the secondary flow passing out of the field shaping unit 500does not mix with the return flow of the primary flow passing down thespiral ramp outside of the outer wall 222.The field shaping unit 500 canhave other configurations that are different than the embodiment shownin FIG. 4. For example, the electrode compartment assembly can have onlya single wall 510 defining a single electrode compartment 520, and thereaction vessel 204 can include only a single electrode 600. The fieldshaping unit of either embodiment still separates the primary andsecondary flows so that the primary flow does not engage the electrode,and thus it shields the workpiece from the single electrode. Oneadvantage of shielding the workpiece from the electrodes 600 a-d is thatthe electrodes can accordingly be much larger than they could be withoutthe field shaping unit because the size of the electrodes does not havean effect on the electrical field presented to the workpiece. This isparticularly useful in situations that use consumable electrodes becauseincreasing the size of the electrodes prolongs the life of eachelectrode, which reduces downtime for servicing and replacingelectrodes.

[0058] An embodiment of reaction vessel 204 shown in FIG. 4 canaccordingly have a first conduit system for conditioning and directingthe primary fluid flow F_(p) to the workpiece, and a second conduitsystem for conditioning and directing the secondary fluid flow F₂. Thefirst conduit system, for example, can include the inlet 320 of thedistributor 300; the channel 324 between the base 412 of the primaryflow guide 400 and the inclined cavity 322 of the distributor 300; aplenum between the wall 422 of the outer baffle 420 and the first wall510 a of the field shaping unit 500; the primary flow guide 400; and theinterior surface 537 of the first lip 536 a. The first conduit systemconditions the direction of the primary fluid flow F_(p) by passing itthrough the primary flow guide 400 and along the interior surface 537 sothat the velocity of the primary flow F_(p) normal to the workpiece isat least substantially uniform across the surface of the workpiece. Theprimary flow F_(p) and the rotation of the workpiece can accordingly becontrolled to influence the mass transfer of electroprocessing medium atthe workpiece.

[0059] The second conduit system, for example, can include the plenum330 and the channels 340-346 of the distributor 300, the walls 510 ofthe field shaping unit 500, and the partitions 530 of the field shapingunit 500. The secondary flow F₂ contacts the electrodes 600 to establishindividual electrical fields in the field shaping unit 500 that areelectrically coupled to the primary flow F_(p.) The field shaping unit500, for example, separates the individual electrical fields created bythe electrodes 600 a-d to create “virtual electrodes” at the top of theopenings defined by the lips 536 a-d of the partitions. In thisparticular embodiment, the central opening inside the first lip 536 adefines a first virtual electrode, the annular opening between the firstand second lips 536 a-b defines a second virtual electrode, the annularopening between the second and third lips 536 b-c defines a thirdvirtual electrode, and the annular opening between the third and fourthlips 536 c-d defines a fourth virtual electrode. These are “virtualelectrodes” because the field shaping unit 500 shapes the individualelectrical fields of the actual electrodes 600 a-d so that the effect ofthe electrodes 600 a-d acts as if they are placed between the top edgesof the lips 536 a-d. This allows the actual electrodes 600 a-d to beisolated from the primary fluid flow, which can provide several benefitsas explained in more detail below.

[0060] An additional embodiment of the processing chamber 200 includesat least one interface member 700 (identified individually by referencenumbers 700 a-d) for further conditioning the secondary flow F₂ ofelectroprocessing solution. The interface members 700, for example, canbe filters that capture particles in the secondary flow that weregenerated by the electrodes (i.e., anodes) or other sources ofparticles. The filter-type interface members 700 can also inhibitbubbles in the secondary flow F₂ from passing into the primary flowF_(p) of electroprocessing solution. This effectively forces the bubblesto pass radially outwardly through the holes 522 in the walls 510 of thefield shaping unit 500. In alternate embodiments, the interface members700 can be ion-membranes that allow ions in the secondary flow F₂ topass through the interface members 700. The ion-membrane interfacemembers 700 can be selected to (a) allow the fluid of theelectroprocessing solution and ions to pass through the interface member700, or (b) allow only the desired ions to pass through the interfacemember such that the fluid itself is prevented from passing beyond theion-membrane.

[0061]FIG. 6 is another isometric view of the reaction vessel 204 ofFIG. 4 showing a cross-sectional portion taken along a differentcross-section. More specifically, the cross-section of FIG. 4 is shownin FIG. 8A and the cross-section of FIG. 6 is shown in FIG. 8B.Returning now to FIG. 6, this illustration further shows one embodimentfor configuring a plurality of interface members 700 a-d relative to thepartitions 530 a-d of the field shaping unit 500. A first interfacemember 700 a can be attached to the skirt 534 of the first partition 530a so that a first portion of the secondary flow F₂ flows past the firstelectrode 600 a, through an opening 535 in the skirt 534, and then tothe first interface member 700 a. Another portion of the secondary flowF₂ can flow past the second electrode 600 b to the second interfacemember 700 b. Similarly, portions of the secondary flow F₂ can flow pastthe third and fourth electrodes 600 c-d to the third and fourthinterface members 700 c-d.

[0062] When the interface members 700 a-d are filters or ion-membranesthat allow the fluid in the secondary flow F₂ to pass through theinterface members 700 a-d, the secondary flow F₂ joins the primary fluidflow Fp. The portion of the secondary flow F₂ in the first electrodecompartment 520 a can pass through the opening 535 in the skirt 534 andthe first interface member 700 a, and then into a plenum between thefirst wall 510 a and the outer wall 422 of the baffle 420. This portionof the secondary flow F₂ accordingly joins the primary flow F_(p) andpasses through the primary flow guide 400. The other portions of thesecondary flow F₂ in this particular embodiment pass through thesecond-fourth electrode compartments 520 b-d and then through theannular openings between the lips 536 a-d. The second-fourth interfacemembers 700 b-d can accordingly be attached to the field shaping unit500 downstream from the second-fourth electrodes 600 b-d.

[0063] In the particular embodiment shown in FIG. 6, the secondinterface member 700 b is positioned vertically between the first andsecond partitions 530 a-b, the third interface member 700 c ispositioned vertically between the second and third partitions 530 b-c,and the fourth interface member 700 d is positioned vertically betweenthe third and fourth partitions 530 c-d. The interface assemblies 710a-d are generally installed vertically, or at least at an upwardlyinclined angle relative to horizontal, to force the bubbles to rise sothat they can escape through the holes 522 in the walls 510 a-d (FIG.4). This prevents aggregations of bubbles that could potentially disruptthe electrical field from an individual electrode.

[0064]FIGS. 7A and 7B illustrate an interface assembly 710 for mountingthe interface members 700 to the field shaping unit 500 in accordancewith an embodiment of the invention. The interface assembly 710 caninclude an annular interface member 700 and a fixture 720 for holdingthe interface member 700. The fixture 720 can include a first frame 730having a plurality of openings 732 and a second frame 740 having aplurality of openings 742 (best shown in FIG. 7A). The holes 732 in thefirst frame can be aligned with the holes 742 in the second frame 740.The second frame can further include a plurality of annular teeth 744extending around the perimeter of the second frame. It will beappreciated that the teeth 744 can alternatively extend in a differentdirection on the exterior surface of the second frame 740 in otherembodiments, but the teeth 744 generally extend around the perimeter ofthe second frame 740 in a top annular band and a lower annular band toprovide annular seals with the partitions 536 a-d (FIG. 6). Theinterface member 700 can be pressed between the first frame 730 and thesecond frame 740 to securely hold the interface member 700 in place. Theinterface assembly 710 can also include a top band 750 a extendingaround the top of the frames 730 and 740 and a bottom band 750 bextending around the bottom of the frames 730 and 740. The top andbottom bands 750 a-b can be welded to the frames 730 and 740 by annularwelds 752. Additionally, the first and second frames 730 and 740 can bewelded to each other by welds 754. It will be appreciated that theinterface assembly 710 can have several different embodiments that aredefined by the configuration of the field shaping unit 500 (FIG. 6) andthe particular configuration of the electrode compartments 520 a-d (FIG.6).

[0065] When the interface member 700 is a filter material that allowsthe secondary flow F₂ of electroprocessing solution to pass through theholes 732 in the first frame 730, the post-filtered portion of thesolution continues along a path (arrow Q) to join the primary fluid flowF_(p) as described above. One suitable material for a filter-typeinterface member 700 is POREX®, which is a porous plastic that filtersparticles to prevent them from passing through the interface member. Inplating systems that use consumable anodes (e.g., phosphorized copper ornickel sulfamate), the interface member 700 can prevent the particlesgenerated by the anodes from reaching the plating surface of theworkpiece.

[0066] In alternate embodiments in which the interface member 700 is anion-membrane, the interface member 700 can be permeable to preferredions to allow these ions to pass through the interface member 700 andinto the primary fluid flow F_(p). One suitable ion-membrane is NAFION®perfluorinated membranes manufactured by DuPont®. Other suitable typesof ion-membranes for plating can be polymers that are permeable to manycations, but reject anions and non-polar species. It will be appreciatedthat in electropolishing applications, the interface member 700 may beselected to be permeable to anions, but reject cations and non-polarspecies. The preferred ions can be transferred through the ion-membraneinterface member 700 by a driving force, such as a difference inconcentration of ions on either side of the membrane, a difference inelectrical potential, or hydrostatic pressure.

[0067] Using an ion-membrane that prevents the fluid of theelectroprocessing solution from passing through the interface member 700allows the electrical current to pass through the interface member whilefiltering out particles, organic additives and bubbles in the fluid. Forexample, in plating applications in which the interface member 700 ispermeable to cations, the primary fluid flow F_(p) can be a catholyteand the secondary fluid flow F₂ can be a separate anolyte because thesefluids do not mix in this embodiment. A benefit of having separateanolyte and catholyte fluid flows is that it eliminates the consumptionof additives at the anodes and thus the need to replenish the additivesas often. Additionally, this feature combined with the “virtualelectrode” aspect of the reaction vessel 204 reduces the need to“burn-in” anodes for insuring a consistent black film over the anodesfor predictable current distribution because the current distribution iscontrolled by the configuration of the field shaping unit 500. Anotheradvantage is that it also eliminates the need to have a predictableconsumption of additives in the secondary flow F₂ because the additivesto the secondary flow F₂ do not effect the primary fluid flow F_(p) whenthe two fluids are separated from each other.

[0068] In another embodiment, the geometry of the reaction vessel 204described above with reference to FIGS. 3-8B is adjusted as themicroelectronic workpiece 101 is processed to actively control thecurrent distribution at the microelectronic workpiece 101 as a functionof time. For example, in one aspect of this embodiment, the distancebetween the microelectronic workpiece 101 and the electrodes 600 a-dand/or the shield 580 is adjusted while current is passing through theelectroprocessing fluid. The distance is changed by moving themicroelectronic workpiece 101, the electrodes 600 a-d, and/or the shield580 toward and away from each other.

[0069] In other embodiments, other methods are used to adjust thegeometry of the reaction vessel 204 during proessing. For example, inone embodiment, the shield 580 (FIG. 4) has an adjustable diaphragmarrangement in which the central opening can change diameter, much likethe aperture of a camera. In another embodiment, the distance betweenthe shield 580 and the microelectronic workpiece 101 is adjusted bymoving the shield 580 and/or the microelectronic workpiece 101 towardand/or away from each other. For example, the shielding provided to theperiphery of the microelectronic workpiece 101 can be reduced duringprocessing by increasing the distance between the workpiece 101 and theshield 580. In yet another embodiment, the openings in the diffuser(positioned between the electrodes 600 a-d and the microelectronicworkpiece 101) are each individually adjustable to change the flowdistribution and/or the overall flow rate of electroprocessing fluid.For example, peripheral openings in the diffuser can be selectivelyclosed or opened to increase or decrease, respectively, the shieldingprovided to the peripheral region of the workpiece 101. In still furtherembodiments, the geometry of the reaction vessel is altered duringprocessing by other methods and/or mechanisms.

[0070] In any of the foregoing embodiments, mechanical changes to thegeometry of the reaction vessel 204 change the distribution of currentat the microelectronic workpiece 101 during processing. In otherembodiments, described below in Section C, the current distribution ischanged by changing the current applied to the electrodes 600 a-d. Theeffects of actively changing the current distribution during processing,by mechanical and/or electrical techniques, are also described ingreater detail below in Section C.

[0071] C. Method of Selecting and Applying Electrical Currents toElectrodes in Reaction Vessels

[0072] FIGS. 9A-9D illustrate processes that can be completed with theapparatuses described above with reference to FIGS. 2-8B by selectivelyadjusting the currents applied to multiple electrodes in processingchambers, for example, to adjust the current distribution in theelectrolytic fluid within the processing chambers. For example, FIG. 9Aillustrates a process 900 that includes contacting a microelectronicworkpiece with an electrolytic fluid (process portion 901) andpositioning a plurality of electrodes in electrical communication withthe electrolytic fluid (process portion 902). The process 900 canfurther include directing a plurality of electrical currents through theplurality of electrodes and changing at least one of the currents in aselected manner during the process. For example, a current ratio of atleast one of the electrical currents to a sum of all of the electricalcurrents can initially have a first current ratio value (process portion903). In process portion 904, the current ratio is changed from thefirst current ratio value to a second current ratio value, and the atleast one electrical current is directed at the second current ratiovalue through one of the electrodes.

[0073] In one embodiment, the current ratio is adjusted between at leasttwo electrodes, and in another embodiment, the current ratio is adjustedover four electrodes. In a further embodiment, the current ratio isadjusted to maintain a current density across the workpiece that variesby less than ten percent of the 3-σ deviation level of a standarddistribution curve. In other embodiments, the variation is less thanfive percent of the 3-σ level. In yet a further embodiment, the firstcurrent ratio value is used while features in a conductive layer of theworkpiece are filled, and the second current ratio value is used while ablanket layer is applied to the filled features.

[0074] In another embodiment, the current distribution over a pluralityof electrodes is adjusted to account for different electrolytic fluidshaving different conductivities. For example, as shown in FIG. 9B, aprocess 910 includes contacting a first microelectronic workpiece with afirst electrolytic fluid having a first conductivity (process portion911) and positioning a plurality of electrodes in electricalcommunication with the first microelectronic workpiece (process portion912). An embodiment of the process 910 further includes directing aplurality of first electrical currents through the plurality ofelectrodes, with a first current distribution as a function of electrodeposition (process portion 913). In process portion 914, a secondmicroelectronic workpiece is placed in contact with a secondelectrolytic fluid having a second conductivity different than the firstconductivity. The process 910 further includes positioning the pluralityof electrodes in electrical communication with the secondmicroelectronic workpiece (process portion 915) and directing aplurality of second electrical currents through the plurality ofelectrodes, with a second current distribution as a function ofelectrode position (process portion 916).

[0075] In other embodiments, the current applied to the electrodes isused to remove conductive material from the workpiece, and/or thieveconductive material that would otherwise attach to the workpiece. Forexample, as shown in FIG. 9C, a process 920 includes contacting amicroelectronic workpiece with an electrolytic fluid (process portion921), removing conductive material from an outer region of a conductivelayer of the workpiece (process portion 922), and then simultaneouslyadding conductive material to both the inner and outer regions of theconductive layer (process portion 923). In another embodiment, shown inFIG. 9D, a process 930 includes contacting the workpiece with anelectrolytic fluid (process portion 931) and directing conductivematerial from a first electrode toward the microelectronic workpiece(process portion 932). The process 930 further includes attracting to asecond electrode at least a portion of the conductive material in theelectrolytic fluid that would otherwise attach to the workpiece, whileadding at least a portion of the conductive material to an inner regionof the workpiece (process portion 933). In one aspect of thisembodiment, the process 930 further includes changing a current appliedto the first electrode as a function of time (process portion 934) andthen simultaneously adding conductive material to both the inner regionand the outer region of the workpiece (process portion 935).

[0076] FIGS. 10A-16 illustrate analytical predictions and experimentalresults for plating conductive materials on microelectronic workpiecesin accordance with several embodiments of the invention that can usemulti-electrode processing chambers generally similar to those describedabove with reference to FIGS. 2-8. The examples described below relateto plating copper blanket layers on copper seed layers, but are alsoapplicable to other materials and other plating operations. The methodsare further applicable to material removal processes.

[0077]FIG. 10A illustrates a table of predicted current levels for eachof four electrodes 600 a-d (FIG. 4) as a function of initial seed layerthickness for a 200 mm workpiece. The predicted current levels areselected to produce a total current in each case of about 6.5 amps, andan instantaneously uniform current density (i.e., a uniform current persquare centimeter of workpiece surface area) across the workpiece 101(FIG. 3). Also shown in FIG. 10A for each initial seed layer thicknessis the percentage of the total current applied to the workpiece 101contributed by each electrode. FIG. 10B is a graphical illustration ofthe current levels for each electrode as a function of the initial seedlayer thickness.

[0078] Referring now to FIGS. 10A and 10B, the percentage of the totalcurrent applied to the inner three electrodes (600 a-c) tends to drop asthe initial seed layer thickness increases. The percentage of the totalcurrent applied to the outermost electrode (600 d) tends to increase asthe initial seed layer thickness increases. It is believed that thisresult is due to the decreasing significance of the terminal effect asthe seed layer thickness increases. For example, compared to a thickseed layer, a relatively thin seed layer will have a higher resistivityand accordingly electrical current will be concentrated near thecontacts around the periphery of the workpiece 101. This will result inhigher plating rates near the contacts than at the center of thin seedlayers. Thus, the current applied to the outermost electrode can belower than that applied to the inner electrodes to counteract theterminal effect If the seed layer is relatively thick, it will have alower resistivity, and, all other variables being equal, the currentdensity will tend to be more uniform over the surface of the workpiece101. Accordingly, FIGS. 10A and 10B indicate that by changing thepercentage of the current passing through each electrode as the seedlayer thickens, a uniform current density over the surface of theworkpiece 101 is obtained.

[0079] The results described above with reference to FIGS. 10A and 10Bare somewhat simplified from an actual deposition process in thatdifferent starting seed layer thicknesses are used to simulate a buildupof conductive material on a given seed layer. For example, the predictedcurrent levels for a 3,000 Å seed layer provide an indication of thecurrent levels that would be required after 2,400 Å of conductivematerial have been built up on a 600 Å seed layer. This is somewhatsimplified from the actual case in that slight non-uniformities that maytend to form during each step of the deposition process may not beaccounted for. FIG. 11, described below, illustrates predicted resultsthat account for at least a portion of this simplification.

[0080]FIG. 11 illustrates predicted current levels as a function of timeapplied to each of four electrodes 600 a-d in a process that begins witha 1000 Å thick seed layer on a 300 mm workpiece, and ends with a 1micron thick blanket layer. The current levels applied to each electrode600 a-d change in six discrete stages. As expected, (based on theresults of FIGS. 10A and 10B) the current applied to the innermostelectrode 600 a tends to decrease over time and the current applied tothe outermost electrode 600 d tends to increase over time. The predictedcurrent applied to the third electrode 600 c tends to decrease overtime, and the predicted current applied to the second electrode 600 btends to increase slightly over time. These results may be due to theeffects neighboring electrodes have on each other, which may be moreaccurately predicted by simulating an entire deposition process on asingle seed layer (as shown in FIG. 11) than by simulating thedeposition process by assuming a series of separate processes, eachstarting with a thicker initial seed layer (as shown in FIGS. 10A and10B).

[0081]FIG. 12 illustrates the predicted film non-uniformity as afunction of film thickness for a six-stage process in accordance with anembodiment of the invention (line 1200) compared with an existingsingle-stage process optimized for uniform current density at a filmthickness of 1 micron. The predictions are for a total current of 15amps transmitted through an electrolytic solution having a conductivityof 511 millisiemens per centimeter (mS/cm). In this prediction, theshield 580 (FIG. 4) has an inner diameter of 290 mm and is positioned 11mm beneath the workpiece 101. The workpiece has an initial seed layerthickness of 1,000 Å. The non-uniformity is indicated as a percentage ofthe 3-σ deviation level of a standard distribution curve (“% 3-σ”). Inother embodiments, the total current changes with time, the conductivityhas other values, and/or the shield 580 has different arrangements.

[0082] As shown in FIG. 12, the multi-stage process indicated by line1200 produces an applied film that is significantly more uniform thanthat resulting from the single-stage process indicated by line 1201, atall thicknesses other than about one micron. For example, in oneembodiment, the multi-stage process produces an applied layer having auniformity of 10% of 3-σ or better. In another embodiment, theuniformity is 5% of 3-σ or better. As is also shown in FIG. 12, thesingle-stage process produces an optimally uniform film at only onepoint (about 1 micron). This is because the single-stage process tendsto overplate the edge of the workpiece 101 in the beginning of theprocess (due to the terminal effect) and underplate the edge of theworkpiece 101 toward the end of the process (to account for the earlieroverplating). If the process continues beyond the design point (e.g.,beyond about 1 micron), the single-stage process will continue tounderplate the edge of the workpiece 101, resulting in an increasinglynon-uniform conductive layer. By contrast, the multi-stage process tendsto produce a uniform layer at all phases of the process, and canaccordingly continue beyond the design point without a substantialincrease in non-uniformity.

[0083]FIG. 13 illustrates predicted current densities as a function ofworkpiece radius at several points in time during an embodiment of themulti-stage process described above with reference to FIGS. 11 and 12.As shown in FIG. 13, the current density is generally uniform (at alevel of from about 20.5 mA/cm² to about 21 mA/cm²) from the center ofthe workpiece 101 to a radius of about 125 mm for all phases of theprocess. At the outer periphery of the workpiece 101, the currentdensity varies between about 19.5 mA/cm² to about 21.5 mA/cm² over thecourse of the process. Accordingly, the current density variation overthe entire workpiece 101 is about 2 mA/cm² (21.5 mA/cm² minus 19.5mA/cm²).

[0084] By way of comparison, FIG. 14 illustrates predicted currentdensities as a function of workpiece radius for an existing single-stageprocess, at the same points in time shown in FIG. 13. As is seen in FIG.14, the existing single-stage process produces a significantly lessuniform current density distribution than does an embodiment of themulti-stage process described above with reference to FIG. 13. Forexample, the current density over the inner 125 mm of the workpiece 101varies from about 17 mA/cm² to about 21.75 mA/cm². The current densityover the outer 25 mm of the workpiece 101 varies from about 19.5 mA/cm²to about 27 mA/cm². Accordingly, the current density variation over theentire workpiece is about 10 mA/cm² (27 mA/cm² minus 17 mA/cm²),significantly greater than the 2 mA/cm² variation described above withreference to FIG. 13.

[0085] One feature of an embodiment of a process described above withreference to FIGS. 10A-13 is that the current passing through eachelectrode (and/or the percentage of the total current contributed byeach electrode) changes during the process. An advantage of thisarrangement is that the local current density at each point on theworkpiece is more uniform throughout the course of the process. As aresult, the layer of conductive material applied to the microelectronicworkpiece 101 is also more uniform at all times. This advantage can haveincreasing significance as the features that are filled by theconductive material decrease in size. For example, while existingprocesses may produce a blanket layer that is uniform at its targetthickness (e.g., at 1 micron, as indicated by line 1201 shown in FIG.12), the non-uniform plating rate during earlier phases of the processmay have significant drawbacks. In particular, the electrolytic solutionmay include additives or other chemicals that promote uniform filmgrowth, but that operate best at selected current densities and/ormaterial application rates. By keeping the current density uniform overthe surface of the workpiece 101 throughout the process, a method inaccordance with an embodiment of the invention increases the likelihoodthat these additives perform well, and reduces the likelihood thatnon-uniformities form in the conductive material applied to theworkpiece 101. The performance of the additives generally becomes moreimportant as the size of the features decreases and the aspect ratio ofthe features increases.

[0086] FIGS. 11-13 (described above) illustrate six-stage processes forproducing uniform blanket layers on generally uniform seed layers. Inother embodiments, the process can have other numbers of stages, otherstarting seed layer shapes and/or other blanket layer shapes. Forexample, FIG. 15 illustrates experimental results for a two-stageprocess that operates on an initially domed seed layer (represented byline 1501). The data shown in FIG. 15 are normalized to the averagethickness at each stage of the process. During a first stage of theprocess, features in the seed layer are filled to produce the profilerepresented by line 1502. Because the shape of line 1502 is similar tothat of line 1501, the current density was uniform during the firststage of the process. During a second stage of the process, material isapplied to the filled seed layer with the current applied to at leastone of the electrodes changed from the level applied during the firststage. At the end of the second stage, the applied layer has a generallyuniform thickness, as represented by line 1503.

[0087] In another embodiment, shown in FIG. 16, the workpiece has aninitially generally flat seed layer profile (indicated by line 1601).The target profile for the blanket layer is indicated by line 1602 andhas a generally concave distribution. Line 1603 indicates an actualprofile produced using a three-stage process and an apparatus generallysimilar to that described above with reference to FIGS. 2-8. In oneaspect of this embodiment, the current was applied to the electrodesaccording to a first distribution during a first stage of the process.The current was changed to a non-DC application after the features ofthe seed layer were filled (during a second stage of the process), anddistribution of the current to the electrodes was changed prior to athird, bulk fill stage of the process.

[0088] In other embodiments, multi-stage processes are used to applymaterial to a variety of different types of seed layers (or other layersor features), to produce a variety of different types of blanket layers(or other layers or features). For example, in one embodiment,multi-stage processes apply material at a generally uniform currentdensity to a generally uniform seed layer, or a concave seed layer, or aconvex seed layer, to produce any of a generally uniform blanket layer,a concave blanket layer, or a convex blanket layer.

[0089] In other embodiments, other characteristics of the materialapplication process are controlled in conjunction with controlling thecurrent applied to each of the electrodes to provide increased controlover the resulting applied conductive layers. For example, in oneembodiment the size of the opening in the shield 580 (FIG. 4) isadjusted to control the electrical field and/or the interaction betweenthe electrolytic fluid and the peripheral region of the microelectronicworkpiece. In another embodiment, the spacing between the shield 580 andthe microelectronic workpiece is adjusted. In still further embodiments,the configuration and/or position of a diffuser in the electrolyticfluid is adjusted to control the electrical field proximate to themicroelectronic workpiece, and/or the interaction between the fluid andthe microelectronic workpiece.

[0090] In yet a further embodiment, the conductivity of the electrolyticsolution in which the microelectronic workpiece is positioned isadjusted and, in one embodiment, has a value of between about 5 mS/cmand about 500 mS/cm. In other embodiments, the conductivity of theelectrolytic fluid has values above or below this range. In oneparticular embodiment, the distribution of current applied to theelectrodes is adjusted as a function of the conductivity of the bath.Accordingly, the distribution of the total current applied to theelectrodes is different when the bath has a low conductivity than whenthe bath has a high conductivity. An advantage of this process is thatthe same processing chamber and electrode arrangement is suitable foruse with electrolytic fluids having a variety of conductivities (with orwithout changing the hardware of the processing chamber) to processdifferent types of workpieces. For example, some workpieces (inparticular, those with very thin starting seed layers) may accumulateadditional conductive material more uniformly when in contact with lowconductivity electrolytic fluids, while the same or other workpieces maybenefit from subsequent process stages that produce better results whenthe workpiece is in contact with high conductivity electrolytic fluids.

[0091] In another embodiment, the current applied to the electrodes isadjusted to add material to one portion of the microelectronic workpieceand remove material from another portion of the microelectronicworkpiece. For example, in one embodiment, the current applied to allthe electrodes 600 a-d is reversed, with the current applied to theouter-most electrode 600 d greater than the current applied to the innerelectrodes 600 a-c. Accordingly, the electrodes 600 a-d operate ascathodes to remove material from the workpiece (and remove material fromthe outer portion of the workpiece more quickly than from the innerportion) to counteract the terminal effect, which would otherwise tendto overplate the peripheral region of the workpiece. After a selectedperiod of time has passed, material is applied to both the inner andouter regions of the workpiece. In another embodiment, the outerelectrode 600 d can operate as a thieving electrode to attractconductive material in the electrolytic solution that would otherwiseplate to the peripheral region of the workpiece. In still anotherarrangement, a separate thieving electrode positioned outwardly from theelectrodes 600 a-d shown in FIG. 4 attracts some of the conductivematerial in the electrolytic fluid while the remaining electrodes platethe remainder of the workpiece. In any of the foregoing embodiments, therate at which conductive material is removed from the microelectronicworkpiece, or thieved prior to attaching to the microelectronicworkpiece, can change during the course of the process.

[0092] In still further embodiments, the process includes other numbersand/or sequences of process stages. For example, in one embodiment thecurrents applied to the electrodes vary continuously rather than indiscrete stages. In other embodiments the current is applied to morethan four electrodes or fewer than four electrodes. In any of theforegoing embodiments in which material is applied to, removed from orthieved from particular regions of the microelectronic workpiece,material may also be applied to, removed from or thieved from,respectively, other regions of the microelectronic workpiece, but at aslower rate. For example, when material is removed from the outer regionof the workpiece, it is preferentially removed from the outer region,but may also be removed from the inner region at a slower or lesspreferential rate.

[0093] From the foregoing, it will be appreciated that specificembodiments of the invention have been described herein for purposes ofillustration, but that various modifications may be made withoutdeviating from the spirit and scope of the invention. Accordingly, theinvention is not limited except as by the appended claims.

I/We claim:
 1. A method for electrolytically processing amicroelectronic workpiece, comprising: contacting the microelectronicworkpiece with an electrolytic fluid; positioning at least one electrodein electrical communication with the electrolytic fluid; directing atleast one electrical current through the at least one electrode toproduce a first current distribution in the electrolytic fluid; andactively changing the first current distribution to produce a secondcurrent distribution in the electrolytic fluid while the microelectronicworkpiece is in contact with the electrolytic fluid, the second currentdistribution being different than the first current distribution.
 2. Themethod of claim 1 wherein the at least one electrode is one of aplurality of electrodes and wherein directing at least one electricalcurrent includes directing a plurality of currents through the pluralityof electrodes.
 3. The method of claim 1 wherein directing at least oneelectrical current includes directing a plurality of electrical currentsthrough a plurality of electrodes with a current ratio of the at leastone of the electrical current to a sum of all of the electrical currentshaving a first current ratio value, and wherein actively changing thefirst current distribution includes directing the plurality ofelectrical currents through the plurality of electrodes with the currentratio having a second current ratio value.
 4. The method of claim 1wherein the microelectronic workpiece has an exposed layer of conductivematerial that is initially generally uniformly thick from a centralregion of the microelectronic workpiece to a peripheral region of themicroelectronic workpiece, and wherein the method further comprisesadding conductive material to the layer to increase a thickness of thelayer at the central region by a first amount and increase the thicknessof the layer at the peripheral region by a second amount greater thanthe first amount.
 5. The method of claim 1 wherein the microelectronicworkpiece has an exposed layer of conductive material that is initiallygenerally uniformly thick from a central region of the microelectronicworkpiece to a peripheral region of the microelectronic workpiece, andwherein the method further comprises adding conductive material to thelayer to increase a thickness of the layer at the central region by afirst amount and increase the thickness of the layer at the peripheralregion by a second amount less than the first amount.
 6. The method ofclaim 1 wherein the microelectronic workpiece has an exposed layer ofconductive material that initially has a thickness with a firstuniformity, and wherein the method further comprises adding conductivematerial to the layer to increase a thickness of the layer and increasea uniformity of the thickness from the first uniformity to a seconduniformity.
 7. The method of claim 1 wherein the microelectronicworkpiece has a layer of conductive material, the layer havingtopographical features, and wherein the method further comprisesdirecting the at least one electrical current to produce the firstcurrent distribution while the topographical features are being filledwith conductive material, and directing the at least one electricalcurrent to produce the second current distribution while conductivematerial is applied to the filled topographical features.
 8. The methodof claim 1 wherein current density is equivalent to current per unitarea of the microelectronic workpiece, and wherein the method furthercomprises providing to a first portion of the microelectronic workpiececurrent at a first current density and providing to a second portion ofthe microelectronic workpiece current at a second current density, thefirst current density being at least approximately the same as thesecond current density, the first and second current densities being atleast approximately equal to each other before and after activelychanging the first current distribution.
 9. The method of claim 1wherein current density is equivalent to current per unit area of themicroelectronic workpiece, and wherein the method further comprises:filling features on the surface of the microelectronic workpiece byapplying a negative potential to the microelectronic workpiece whiledirecting the electrical currents through the plurality of electrodes;and building a layer of conductive material on the microelectronicworkpiece after the features have been filled by applying a negativepotential to the microelectronic workpiece, wherein a current densitydistribution across a surface of the microelectronic workpiece isapproximately the same while filling the features and while building thelayer of conductive material.
 10. The method of claim 1, wherein currentdensity is equivalent to current per unit area of the microelectronicworkpiece, and wherein the method further comprises: filling features onthe surface of the microelectronic workpiece by providing to themicroelectronic workpiece current at an approximately constant currentdensity over the surface of the microelectronic workpiece; and applyingcurrent to the microelectronic workpiece at a spatially varying currentdensity to form a conductive layer having a selected shape.
 11. Themethod of claim 1, wherein current density is equivalent to current perunit area of the microelectronic workpiece, and wherein the methodfurther comprises: filling features on the surface of themicroelectronic workpiece by providing to the microelectronic workpiececurrent at an approximately constant current density over the surface ofthe microelectronic workpiece; and applying current to themicroelectronic workpiece at a spatially varying current density to forma conductive layer having a generally concave profile, a generallyconvex profile or a generally flat profile.
 12. The method of claim 1wherein current density is equivalent to current per unit area of themicroelectronic workpiece, and wherein directing at least one electricalcurrent includes providing a first electrical current to an innerportion of the microelectronic workpiece at a first current density thatis at least approximately constant with time, and providing a secondelectrical current to an outer portion of the microelectronic workpieceat a second current density that is at least approximately constant withtime and that is at least approximately the same as the first currentdensity.
 13. The method of claim 1, further comprising positioning ashield adjacent to the least one electrode while the microelectronicworkpiece contacts the electrolytic fluid, and wherein actively changingthe first current distribution includes changing a configuration and/orrelative position of the shield while the first microelectronicworkpiece is in contact with the electrolytic fluid.
 14. A method forelectrolytically processing a microelectronic workpiece, comprising:contacting the microelectronic workpiece with an electrolytic fluid;positioning a plurality of electrodes in electrical communication withthe electrolytic fluid; directing a plurality of electrical currentsthrough the plurality of electrodes with a current ratio of at least oneof the electrical currents to a sum of all of the electrical currentshaving a first current ratio value; and directing the plurality ofelectrical currents through the plurality of electrodes with the currentratio having a second current ratio value.
 15. The method of claim 14wherein the plurality of electrodes includes four electrodes, andwherein the method further comprises changing a current passing througheach of the four electrodes while the electrodes are in fluid andelectrical communication with the microelectronic workpiece.
 16. Themethod of claim 14 wherein the microelectronic workpiece has an exposedlayer of conductive material that is initially generally uniformly thickfrom a central region of the microelectronic workpiece to a peripheralregion of the microelectronic workpiece, and wherein the method furthercomprises adding conductive material to the layer to increase athickness of the layer at the central region by a first amount andincrease the thickness of the layer at the peripheral region by a secondamount greater than the first amount.
 17. The method of claim 14 whereinthe microelectronic workpiece has an exposed layer of conductivematerial that is initially generally uniformly thick from a centralregion of the microelectronic workpiece to a peripheral region of themicroelectronic workpiece, and wherein the method further comprisesadding conductive material to the layer to increase a thickness of thelayer at the central region by a first amount and increase the thicknessof the layer at the peripheral region by a second amount less than thefirst amount.
 18. The method of claim 14 wherein the microelectronicworkpiece has an exposed layer of conductive material that initially hasa thickness with a first uniformity, and wherein the method furthercomprises adding conductive material to the layer to increase athickness of the layer and increase a uniformity of the thickness fromthe first uniformity to a second uniformity.
 19. The method of claim 14wherein the microelectronic workpiece has a layer of conductivematerial, the layer having topographical features, further comprisingselecting the current ratio to have the first current ratio value whilethe topographical features are being filled with conductive material,and selecting the current ratio to have the second current ratio valuewhile conductive material is applied to the filled topographicalfeatures, the first current ratio value being different than the secondcurrent ratio value.
 20. The method of claim 14 wherein directing theplurality of electrical currents with the current ratio having a secondcurrent ratio value includes changing the current ratio while themicroelectronic workpiece is in electrical communication with theplurality of electrodes.
 21. The method of claim 14 wherein currentdensity is equivalent to current per unit area of the microelectronicworkpiece, and wherein the method further comprises providing to a firstportion of the microelectronic workpiece current at a first currentdensity and providing to a second portion of the microelectronicworkpiece current at a second current density, the first current densitybeing at least approximately the same as the second current density. 22.The method of claim 14 wherein current density is equivalent to currentper unit area of the microelectronic workpiece, and wherein the methodfurther comprises: filling features on a surface of the microelectronicworkpiece by applying a negative potential to the microelectronicworkpiece while directing the electrical currents through the pluralityof electrodes; and building a layer of conductive material on themicroelectronic workpiece after the features have been filled byapplying a negative potential to the microelectronic workpiece, whereina current density distribution across a surface of the microelectronicworkpiece is approximately the same while filling the features and whilebuilding the layer of conductive material.
 23. The method of claim 14,wherein current density is equivalent to current per unit area of themicroelectronic workpiece, and wherein the method further comprises:filling features on a surface of the microelectronic workpiece byproviding to the microelectronic workpiece current at an approximatelyconstant current density over the surface of the microelectronicworkpiece; and applying current to the microelectronic workpiece at aspatially varying current density to form a conductive layer having aselected shape.
 24. The method of claim 14, wherein current density isequivalent to current per unit area of the microelectronic workpiece,and wherein the method further comprises: filling features on a surfaceof the microelectronic workpiece by providing to the microelectronicworkpiece current at an approximately constant current density over thesurface of the microelectronic workpiece; and applying current to themicroelectronic workpiece at a spatially varying current density to forma conductive layer having a generally concave profile, a generallyconvex profile or a generally flat profile.
 25. The method of claim 14wherein current density is equivalent to current per unit area of themicroelectronic workpiece, and wherein directing a plurality ofelectrical currents includes providing a first electrical current to aninner portion of the microelectronic workpiece at a first currentdensity that is at least approximately constant with time, and providinga second electrical current to an outer portion of the microelectronicworkpiece at a second current density that is at least approximatelyconstant with time and that is at least approximately the same as thefirst current density.
 26. The method of claim 14, further comprisingchanging the current ratio in a generally monotonic, incremental mannerbetween the first current ratio value and the second current ratiovalue.
 27. The method of claim 14 wherein the plurality of electrodesincludes a first electrode in electrical communication with a firstportion of the microelectronic workpiece and a second electrode inelectrical communication with a second portion of the microelectronicworkpiece positioned outwardly from the first portion, and wherein themethod further comprises decreasing an electrical current applied to thefirst electrode relative to an electrical current applied to the secondelectrode and/or increasing an electrical current applied to the secondelectrode relative to an electrical current applied to the firstelectrode.
 28. The method of claim 14, further comprising applying acopper material to the microelectronic workpiece in an electrolyticdeposition process.
 29. The method of claim 14, further comprisingapplying to the microelectronic workpiece at least one of a metal and ametal alloy in an electrolytic deposition process.
 30. The method ofclaim 14 wherein the plurality of electrodes function as anodes andwherein the microelectronic workpiece functions as a cathode, andwherein the method further comprises adding electrically conductivematerial to the microelectronic workpiece.
 31. The method of claim 14wherein the plurality of electrodes function as cathodes and wherein themicroelectronic workpiece functions as an anode, and wherein the methodfurther comprises removing electrically conductive material from themicroelectronic workpiece.
 32. The method of claim 14 wherein directingthe electrical currents through the electrolytic fluid includesdirecting the electrical currents through an electrolytic fluid having aconductivity of from about 5 mS/cm to about 500 mS/cm.
 33. The method ofclaim 14 wherein the microelectronic workpiece is a firstmicroelectronic workpiece, and wherein the method further compriseschanging a conductivity of the electrolytic fluid after contacting thefirst microelectronic workpiece with the electrolytic fluid and beforecontacting a second microelectronic workpiece with the electrolyticfluid.
 34. The method of claim 14 wherein the microelectronic workpieceis a first microelectronic workpiece, and wherein the method furthercomprises: positioning a shield adjacent to at least one of theelectrodes while the first microelectronic workpiece contacts theelectrolytic fluid; and changing a configuration and/or relativeposition of the shield after contacting the first microelectronicworkpiece with the electrolytic fluid and before contacting a secondmicroelectronic workpiece with the electrolytic fluid.
 35. The method ofclaim 14 wherein the sum of the electrical currents remains constant asthe current ratio changes.
 36. The method of claim 14 wherein the sum ofthe electrical currents changes as the current ratio changes.
 37. Amethod for electrolytically processing a microelectronic workpiece,comprising: contacting the microelectronic workpiece with anelectrolytic fluid; positioning a plurality of electrodes and electricalcommunication with the electrolytic fluid, the plurality of electrodesincluding a first electrode and a second electrode; directing a firstelectrical current through the first electrode and a first portion ofthe microelectronic workpiece; directing a second electrical currentthrough the second electrode and a second portion of the microelectronicworkpiece while the first electrical current is directed through thefirst electrode and the first portion of the microelectronic workpiece,wherein a first current ratio of the first electrical current to a sumof the first and second electrical currents has a first value, andwherein a second current ratio of the second electrical current to a sumof the first and second electrical currents has a second value; changingthe first current ratio from the first value to a third value anddirecting the first electrical current at the third value; and changingthe second current ratio from the second value to a fourth value anddirecting the second electrical current at the fourth value.
 38. Themethod of claim 37 wherein the microelectronic workpiece has a layer ofconductive material, the layer having topographical features, andwherein changing the first current ratio includes selecting the firstcurrent ratio to have the first value while the topographical featuresare being filled with conductive material, and selecting the firstcurrent ratio to have the third value while conductive material isapplied to the filled topographical features, the first value beingdifferent than the third value.
 39. The method of claim 37, furthercomprising: directing a fifth electrical current through theelectrolytic fluid between a third electrode and a third portion of themicroelectronic workpiece while directing the first and secondelectrical currents; and directing a sixth electrical current throughthe electrolytic fluid between a fourth electrode and a fourth portionof the microelectronic workpiece while directing the first and secondelectrical currents.
 40. The method of claim 37 wherein current densityis equivalent to current per unit area of the microelectronic workpiece,and wherein the method further comprises providing to the first portionof the microelectronic workpiece current at a first current density andproviding to the second portion of the microelectronic workpiece currentat a second density, the first current density being at leastapproximately the same as the second current density.
 41. The method ofclaim 37 wherein the second portion of the microelectronic workpiece ispositioned outwardly from the first portion of the microelectronicworkpiece, and wherein changing the first current ratio includesdecreasing an electrical current applied to the first electrode relativeto an electrical current applied to the second electrode and/orincreasing an electrical current applied to the second electroderelative to an electrical current applied to the first electrode. 42.The method of claim 37 wherein directing the first electrical currentthrough the electrolytic fluid includes directing the first electricalcurrent through an electrolytic solution having a conductivity of fromabout 5 mS/cm to about 500 mS/cm.
 43. The method of claim 37 whereindirecting the first electrical current through the electrolytic fluidincludes directing the first electrical current through an electrolyticfluid having a conductivity of about 5 mS/cm or less to about 500 mS ormore.
 44. A method for electrolytically processing a microelectronicworkpiece, comprising: contacting a surface of the microelectronicworkpiece with an electrolytic fluid; positioning a plurality ofelectrodes in electrical communication with the microelectronicworkpiece, the plurality of electrodes including at least a firstelectrode and a second electrode; directing a first electrical currentthrough the electrolytic fluid between the first electrode and a firstportion of the microelectronic workpiece; directing a second electricalcurrent through the electrolytic fluid between the second electrode anda second portion of the microelectronic workpiece while the firstelectrical current is directed between the first electrode and the firstportion of the microelectronic workpiece; varying the first and secondelectrical currents as a function of time while directing the first andsecond electrical currents and while the microelectronic workpiececontacts the electrolytic fluid; while the first electrical currentvaries with time, providing the first electrical current at a currentdensity per unit area of the microelectronic workpiece that varies byless than about 10% of a 3σ value over the surface of themicroelectronic workpiece; and while the second electrical currentvaries with time, providing the second electrical current at a currentdensity per unit area of the microelectronic workpiece that varies byless than about 10% of a 3σ value over the surface of themicroelectronic workpiece.
 45. The method of claim 44 wherein providingthe first electrical current includes providing the first electricalcurrent at a current density per unit area of the microelectronicworkpiece that varies by less than about 5% of a 3σ value over thesurface of the microelectronic workpiece, and wherein providing thesecond electrical current includes providing the second electricalcurrent at a current density per unit area of the microelectronicworkpiece that varies by less than about 5% of a 3σ value over thesurface of the microelectronic workpiece.
 46. The method of claim 44wherein the second portion of the microelectronic workpiece is disposedoutwardly from the first portion, and wherein varying the firstelectrical current as a function of time includes changing a ratio ofthe first electrical current to a sum of the first and second electricalcurrents, further wherein varying the second electrical current as afunction of time includes changing a ratio of the second current to asum of the first and second electrical currents.
 47. The method of claim44 wherein varying the first and second electrical currents as afunction of time includes temporally changing a ratio of the firstelectrical current to a sum of electrical currents passing through allelectrodes in fluid and electrical communication with themicroelectronic workpiece and temporally changing a ratio of the secondelectrical current to the sum electrical currents passing through allelectrodes in fluid and electrical communication with themicroelectronic workpiece.
 48. The method of claim 44 wherein themicroelectronic workpiece has a layer of conductive material, the layerhaving topographical features, the layer having a thickness that isdifferent at an inner portion of the microelectronic workpiece than atan outer portion of the microelectronic workpiece, and wherein varyingthe first and second electrical currents as a function of time includesselecting a ratio of the first electrical current to a first sum of allelectrical currents passing through the microelectronic workpiece tohave a first value while the topographical features are being filledwith conductive material, and selecting a ratio of the first electricalcurrent to a second sum of all electrical currents passing through themicroelectronic workpiece to have a second value while conductivematerial is applied to the filled topographical features, the firstvalue being different than the second value.
 49. The method of claim 44wherein varying the first and second electrical currents as a functionof time includes applying to the first electrode a current at a firstvalue while filling features on a surface of the microelectronicworkpiece, and applying to the first electrode a current at a secondvalue while building a layer of conductive material on themicroelectronic workpiece after the features have been filled.
 50. Themethod of claim 44, further comprising: directing a third electricalcurrent through the electrolytic fluid between a third electrode and athird portion of the microelectronic workpiece; directing a fourthelectrical current through the electrolytic fluid between a fourthelectrode and a fourth portion of the microelectronic workpiece; andvarying the third and fourth electrical currents as a function of timewhile directing the third and fourth electrical currents and while themicroelectronic workpiece contacts the electrolytic fluid.
 51. Themethod of claim 44 wherein the first and second portions of themicroelectronic workpiece are disposed outwardly from a third and fourthportion of the microelectronic workpiece, and wherein a third electrodeis positioned in fluid and electrical communication with the thirdportion, further wherein a fourth electrode is positioned in fluid andelectrical communication with the fourth portion, and wherein the methodfurther comprises providing to the first and second portions of themicroelectronic workpiece current at a first current per unit area ofthe microelectronic workpiece and providing to the fourth portion of themicroelectronic workpiece current at a second current per unit area ofthe microelectronic workpiece, the first current per unit area being atleast approximately constant while the first and second electrodes arein electrical communication with the microelectronic workpiece, thesecond current per unit area temporally varying while the fourthelectrode is in electrical communication with the microelectronicworkpiece.
 52. The method of claim 44, further comprising: fillingfeatures on a surface of the microelectronic workpiece by applying anegative potential to the microelectronic workpiece while directing thefirst and second currents; and building a layer of conductive materialon the microelectronic workpiece after the features have been filled byapplying a negative potential to the microelectronic workpiece whiledirecting the first and second currents, wherein a current per unit areaof the of the microelectronic workpiece is approximately the same whilefilling the features and while building the layer of conductivematerial.
 53. The method of claim 44 wherein directing the firstelectrical current through the electrolytic fluid includes directing thefirst electrical current through an electrolytic solution having aconductivity of about 5 mS/cm to about 500 mS/cm.
 54. A method forelectrolytically processing a microelectronic workpiece, comprising:contacting a surface of the microelectronic workpiece with anelectrolytic fluid; positioning a plurality of electrodes in electricalcommunication with the microelectronic workpiece, the plurality ofelectrodes including at least a first electrode and a second electrode;directing a first electrical current through the electrolytic fluidbetween a first electrode and a first portion of the microelectronicworkpiece; directing a second electrical current through theelectrolytic fluid between a second electrode and a second portion ofthe microelectronic workpiece while the first electrical current isdirected between the first electrode and the first portion of themicroelectronic workpiece; applying the first electrical current at afirst value while filling features of the microelectronic workpiece withconductive material, then applying the first electrical current at asecond value different than the first value while applying conductivematerial to the filled features; and applying the second electricalcurrent at a first value while filling features of the microelectronicworkpiece with conductive material, then applying the second electricalcurrent at a second value while applying conductive material to thefilled features, wherein a ratio of the first value of the first currentto a sum of the first values of the first and second currents isdifferent than a ratio of the second value of the first current to a sumof the second values of the first and second currents.
 55. The method ofclaim 54, further comprising changing a ratio of the first electricalcurrent to the sum of the first and second electrical currents as afunction of time and changing a ratio of the second electrical currentto the sum of the first and second electrical currents as a function oftime.
 56. The method of claim 54 wherein the first electrode is inelectrical communication with a first portion of the microelectronicworkpiece and the second electrode is in electrical communication with asecond portion of the microelectronic workpiece positioned outwardlyfrom the first portion, and wherein the method further comprisesdecreasing an electrical current applied to the first electrode relativeto an electrical current applied to the second electrode and/orincreasing an electrical current applied to the second electroderelative to an electrical current applied to the first electrode. 57.The method of claim 54 wherein directing the first electrical currentthrough the electrolytic fluid includes directing the first electricalcurrent through an electrolytic solution having a conductivity of fromabout 5 mS/cm to about 500 mS/cm.
 58. The method of claim 54 whereindirecting the first electrical current through the electrolytic fluidincludes directing the first electrical current through an electrolyticfluid having a conductivity of about 5 mS/cm or less to about 500 mS/cmor more.
 59. A method for electrolytically processing a microelectronicworkpiece, comprising: contacting the microelectronic workpiece with anelectrolytic fluid, the microelectronic workpiece having an innerregion, an outer region disposed outwardly from the inner region, and aconductive layer disposed on the inner region and the outer region;removing conductive material from the conductive layer in the outerregion cover zero or non-zero; and after removing conductive materialfrom the conductive layer in the outer region, simultaneously addingconductive material to the conductive layer in both the outer region andthe inner region.
 60. The method of claim 59 wherein removing conductivematerial from the conductive layer in the outer region includes removingconductive material at a first rate, and wherein the method furthercomprises removing conductive material from the conductive layer in theinner region at a second rate less than the first rate.
 61. The methodof claim 59, further comprising adding conductive material to theconductive layer in the inner region and the outer region prior toremoving conductive material from the conductive layer.
 62. The methodof claim 59, further comprising positioning first and second electrodesin electrical communication with the microelectronic workpiece, thefirst electrode being disposed inwardly from the second electrode, andwherein removing conductive material in the outer region while addingconductive material to the conductive layer in the inner region includesremoving material to the second electrode and adding conductive materialfrom the first electrode.
 63. The method of claim 59 whereinsimultaneously adding conductive material to the conductive layer inboth the outer region and the inner region includes directing a firstcurrent through the electrolytic fluid between a first electrode and theinner region and directing a second current through the electrolyticfluid between a second electrode and the outer region.
 64. The method ofclaim 59 wherein simultaneously adding conductive material to theconductive layer in both the outer region and the inner region includesdirecting a first current through the electrolytic fluid between a firstelectrode and the inner region, directing a second current through theelectrolytic fluid between a second electrode and the outer region, andvarying the first and second currents over time while themicroelectronic workpiece contacts the electrolytic fluid.
 65. A methodfor electrolytically processing a microelectronic workpiece, comprising:contacting the microelectronic workpiece with an electrolytic fluid, themicroelectronic workpiece having an inner region, an outer regiondisposed outwardly from the inner region, and a conductive layerdisposed on the inner region and the outer region; directing conductivematerial from a first electrode toward the microelectronic workpiece;attracting to a second electrode spaced apart from the first electrodeand the microelectronic workpiece at least a portion of the conductivematerial in the electrolytic fluid that would otherwise attach to themicroelectronic workpiece; while attracting at least a portion of theconductive material to the second electrode, adding at least a portionof the conductive material to the conductive layer in at least the innerregion; changing a current applied to the first electrode as a functionof time; and after attracting at least a portion of the conductivematerial to the second electrode, simultaneously adding conductivematerial to the conductive layer in both the outer region and the innerregion.
 66. The method of claim 65 wherein attracting to the secondelectrode at least a portion of the conductive material includeschanging a rate at which at least a portion of the conductive materialis attracted to the second electrode.
 67. The method of claim 65 whereinsimultaneously adding conductive material to the conductive layer inboth the outer region and the inner region includes directing a firstcurrent through the electrolytic fluid between a first electrode and theinner region, directing a second current through the electrolytic fluidbetween a second electrode and the outer region, and varying the firstand second currents over time while the microelectronic workpiececontacts the electrolytic fluid.
 68. The method of claim 65 whereinsimultaneously adding conductive material in both the outer region andthe inner region includes applying a first electrical current to thefirst electrode and applying a second electrical current to the secondelectrode, and wherein changing a current applied to the first electrodeincludes changing a ratio of the first electrical current to a sum ofthe first and second electrical currents as a function of time.
 69. Amethod for electrolytically processing a microelectronic workpiece,comprising: contacting a surface of a microelectronic workpiece with anelectrolytic fluid; directing a plurality of electrical currents from acorresponding plurality of electrodes through the electrolytic fluid andto a corresponding plurality of portions of the microelectronicworkpiece; for each electrical current, varying a ratio of theelectrical current to a sum of electrical currents applied to themicroelectronic workpiece; and for each portion of the microelectronicworkpiece at any point in time, maintaining a current density per unitarea of the microelectronic workpiece at approximately the same valuewhile the microelectronic workpiece contacts the electrolytic fluid. 70.The method of claim 69, further comprising maintaining approximately thesame current density per unit area of the microelectronic workpiecewhile features are being filled and while the conductive material isapplied to the filled features.
 71. A system for electrolyticallyprocessing a microelectronic workpiece, comprising: a processing stationhaving a vessel configured to carry an electrolytic fluid, theprocessing station further having at least one contact and at least oneelectrode configured to be in electrical communication with themicroelectronic workpiece to produce a first current distribution at asurface of the microelectronic workpiece; and a device operativelycoupled to the processing station to actively change the first currentdistribution and produce a second current distribution at the surface ofthe microelectronic workpiece while the microelectronic workpiece is incontact with the electrolytic fluid, the second current distributionbeing different than the first current distribution.
 72. The system ofclaim 71 wherein the at least one electrode is one of a plurality ofelectrodes and wherein the device includes a controller having acomputer operable medium with contents capable of: directing a pluralityof electrical currents through the plurality of electrodes, with acurrent ratio of at least one of the electrical currents to a sum of allof the electrical currents having a first current ratio value; andchanging the current ratio from the first current ratio value to asecond current ratio value and directing the at least one electricalcurrent at the second current ratio value through one of the electrodes.73. The system of claim 71 wherein the microelectronic workpiece has alayer of conductive material, the layer having topographical features,and wherein the at least one electrode is one of a plurality ofelectrodes, further wherein the at least one electrode is one of aplurality of electrodes and wherein the device includes a controllerhaving a computer operable medium with contents capable of: directing aplurality of electrical currents through the plurality of electrodes,with a current ratio of at least one of the electrical currents to a sumof all of the electrical currents having a first current ratio value;and changing the current ratio from the first current ratio value to asecond current ratio value and directing the at least one electricalcurrent at the second current ratio value through one of the electrodeswith the current ratio of the at least one electrical current having thefirst value while the topographical features are being filled withconductive material, and having the second value while conductivematerial is applied to the filled topographical features, the firstvalue being different than the second value.
 74. A system forelectrolytically processing a microelectronic workpiece, comprising: aprocessing station having a vessel configured to carry an electrolyticfluid, the processing station further having at least one contact and aplurality of electrodes, all configured to be in electricalcommunication with the microelectronic workpiece; and a controllerhaving a computer operable medium with contents capable of: directing aplurality of electrical currents through the plurality of electrodes,with a current ratio of at least one of the electrical currents to a sumof all of the electrical currents having a first current ratio value;and changing the current ratio from the first current ratio value to asecond current ratio value and directing the at least one electricalcurrent at the second current ratio value through one of the electrodes.75. The system of claim 74 wherein the plurality of electrodes includesfour electrodes, and wherein the computer operable medium has contentscapable of changing a current passing through each of the fourelectrodes while the electrodes are in electrical communication with themicroelectronic workpiece.
 76. The system of claim 74 wherein themicroelectronic workpiece has a layer of conductive material, the layerhaving topographical features, and wherein the computer operable mediumhas contents capable of directing the electrical currents with thecurrent ratio of the at least one electrical current having the firstvalue while the topographical features are being filled with conductivematerial, and having the second value while conductive material isapplied to the filled topographical features, the first value beingdifferent than the second value.
 77. The system of claim 74 wherein thecomputer operable medium is capable of changing the current ratio in agenerally monotonic, incremental manner between the first current ratiovalue and the second current ratio value.
 78. The system of claim 74wherein computer operable medium is capable of maintaining the sum ofthe electrical currents constant as the current ratio changes.
 79. Thesystem of claim 74 wherein the computer readable medium is capable ofchanging the sum of the electrical currents as the current ratiochanges.
 80. The system of claim 74 wherein the computer readable mediumis capable of directing the plurality of electrical currents to fillfeatures on a surface of the microelectronic workpiece by providing tothe microelectronic workpiece current at an approximately constantcurrent density over the surface of the microelectronic workpiece andapply current to the microelectronic workpiece at a spatially varyingcurrent density to form a conductive layer having a selected shape. 81.A system for electrolytically processing a microelectronic workpiece,comprising: a processing station having a vessel configured to carry anelectrolytic fluid, the processing station further having at least onecontact and a plurality of electrodes, all configured to be inelectrical communication with the microelectronic workpiece; and acontroller having a computer operable medium with contents capable of:directing a first electrical current through first electrode and a firstportion of the microelectronic workpiece; directing a second electricalcurrent through the second electrode and a second portion of themicroelectronic workpiece while the first electrical current is directedthrough the first electrode and the first portion of the microelectronicworkpiece, wherein a first current ratio of the first electrical currentto a sum of the first and second electrical currents has a first value,and wherein a second current ratio of the second electrical current to asum of the first and second electrical currents has a second value;changing the first current ratio from the first value to a third valueand directing the first electrical current at the third value; andchanging the second current ratio from the second value to a fourthvalue and directing the second electrical current at the fourth value.82. The system of claim 81 wherein the microelectronic workpiece has alayer of conductive material, the layer having topographical features,and wherein the computer operable medium is capable of directing currentwith the first current ratio having the first value while thetopographical features are being filled with conductive material, andhaving the third value while conductive material is applied to thefilled topographical features, the first value being different than thethird value.
 83. The system of claim 81 wherein current density isequivalent to current per unit area of the microelectronic workpiece,and wherein the computer operable medium is capable of providing to thefirst portion of the microelectronic workpiece current at a firstcurrent density and providing to the second portion of themicroelectronic workpiece current at a second density, the first currentdensity being at least approximately the same as the second currentdensity.
 84. The system of claim 81 wherein the second portion of themicroelectronic workpiece is positioned outwardly from the first portionof the microelectronic workpiece, and wherein the computer operablemedium is capable of decreasing an electrical current applied to thefirst electrode relative to an electrical current applied to the secondelectrode and/or increasing an electrical current applied to the secondelectrode relative to an electrical current applied to the firstelectrode.
 85. A system for electrolytically processing amicroelectronic workpiece, comprising: a processing station having avessel configured to carry an electrolytic fluid, the processing stationfurther having at least one contact and a plurality of electrodes, allconfigured to be in electrical communication with the microelectronicworkpiece, the plurality of electrodes including at least a firstelectrode and a second electrode; and a controller having a computeroperable medium with contents capable of: directing a first electricalcurrent through the electrolytic fluid between the first electrode and afirst portion of the microelectronic workpiece; directing a secondelectrical current through the electrolytic fluid between the secondelectrode and a second portion of the microelectronic workpiece whilethe first electrical current is directed between the first electrode andthe first portion of the microelectronic workpiece; varying the firstand second electrical currents as a function of time while directing thefirst and second electrical currents and while the microelectronicworkpiece contacts the electrolytic fluid; while the first electricalcurrent varies with time, providing the first electrical current at acurrent density per unit area of the microelectronic workpiece thatvaries by less than about 10% of a 3σ value over the surface of themicroelectronic workpiece; and while the second electrical currentvaries with time, providing the second electrical current at a currentdensity per unit area of the microelectronic workpiece that varies byless than about 10% of a 3σ value over the surface of themicroelectronic workpiece.
 86. The system of claim 85 wherein the secondportion of the microelectronic workpiece is disposed outwardly from thefirst portion, and wherein the computer operable medium is capable ofchanging a ratio of the first electrical current to a sum of the firstand second electrical currents, and changing a ratio of the secondcurrent to a sum of the first and second electrical currents.
 87. Thesystem of claim 85 wherein the computer operable medium is capable ofdirecting to the first electrode a current at a first value whilefeatures on a surface of the microelectronic workpiece are being filled,and directing to the first electrode a current at a second value while alayer of conductive material is built on the microelectronic workpieceafter the features have been filled.
 88. A system for electrolyticallyprocessing a microelectronic workpiece, comprising: a processing stationhaving a vessel configured to carry an electrolytic fluid, theprocessing station further having at least one contact and a pluralityof electrodes, all configured to be in electrical communication with themicroelectronic workpiece; and a controller having a computer operablemedium with contents capable of: directing a first electrical currentthrough the electrolytic fluid from one of a first electrode and a firstportion of the microelectronic workpiece to the other; directing asecond electrical current through the electrolytic fluid from one of asecond electrode and a second portion of the microelectronic workpieceto the other while the first electrical current is directed between thefirst electrode and the first portion of the microelectronic workpiece;directing the first electrical current at a first value while fillingfeatures of the microelectronic workpiece with conductive material, thenapplying the first electrical current at a second value different thanthe first value while applying conductive material to the filledfeatures; and directing the second electrical current at a first valuewhile filling features of the microelectronic workpiece with conductivematerial, then applying the second electrical current at a second valuewhile applying conductive material to the filled features, wherein aratio of the first value of the first current to a sum of the firstvalues of the first and second currents is different than a ratio of thesecond value of the first current to a sum of the second values of thefirst and second currents.
 89. The system of claim 88 wherein thecomputer operable medium is capable of changing a ratio of the firstelectrical current to the sum of the first and second electricalcurrents as a function of time and changing a ratio of the secondelectrical current to the sum of the first and second electricalcurrents as a function of time.
 90. A system for electrolyticallyprocessing a microelectronic workpiece, comprising: a processing stationhaving a vessel configured to carry an electrolytic fluid, theprocessing station further having at least one contact and a pluralityof electrodes, all configured to be in electrical communication with themicroelectronic workpiece; and a controller having a computer operablemedium with contents capable of: directing first electrical currentsthrough at least one of the plurality of electrodes to remove conductivematerial from an outer region of a conductive layer of themicroelectronic workpiece; and after removing conductive material fromthe conductive layer in the outer region, directing second electricalcurrents through at least one of the plurality of electrodes tosimultaneously add conductive material to the conductive layer in boththe outer region and the inner region of the conductive layer.
 91. Thesystem of claim 90 wherein the computer operable medium is capable ofdirecting currents for simultaneously adding conductive material to theconductive layer in both the outer region and the inner region bydirecting a first current through the electrolytic fluid between a firstelectrode and the inner region and directing a second current throughthe electrolytic fluid between a second electrode and the outer region.92. The system of claim 90 wherein the computer operable medium iscapable of directing currents for simultaneously adding conductivematerial to the conductive layer in both the outer region and the innerregion by directing a first current through the electrolytic fluidbetween a first electrode and the inner region, directing a secondcurrent through the electrolytic fluid between a second electrode andthe outer region, and varying the first and second currents over timewhile the microelectronic workpiece contacts the electrolytic fluid. 93.A system for electrolytically processing a microelectronic workpiece,comprising: a processing station having a vessel configured to carry anelectrolytic fluid, the processing station further having at least onecontact and a plurality of electrodes configured to carry a plurality ofelectrical currents, wherein the at least one contact and the pluralityof electrodes are configured to be in electrical communication with themicroelectronic workpiece; and a controller having a computer operablemedium with contents capable of: for each electrical current, varying aratio of the electrical current to a sum of electrical currents appliedto the microelectronic workpiece; and for each portion of themicroelectronic workpiece at any point in time, maintaining a currentdensity per unit area of the microelectronic workpiece at approximatelythe same value while the microelectronic workpiece contacts theelectrolytic fluid.
 94. The system of claim 93 wherein the computeroperable medium is capable of directing currents for maintainingapproximately the same current density per unit area of themicroelectronic workpiece while features are being filled and while theconductive material is applied to the filled features.